Centrifugation allows to separate components of very variable size and mass contained in a liquid sample, from molecules to entire cells.
Indeed, the putting into rotation of a rotor carrying a container containing this liquid sample generates a centrifugal force that produces an acceleration that is exerted radially outwardly of the axis of rotation.
Hence, for a given component, by choosing correctly the speed of rotation, the acceleration obtained becomes predominant with respect to the molecular agitation, which causes its settling to the bottom of the container or its rising up to the surface.
For the implementation of this technique, a laboratory centrifuge is used, which comprises:                a driving shaft, associated with motor means,        a rotor removably mounted on said driving shaft, intended to receive the liquid samples to be centrifuged,        a shielded bowl surrounding the rotor, delimiting an access opening,        a casing that carries the shielded bowl, and        a lid mobile between a closed position to close said access opening and an open position to clear said access opening, this lid being carried by and articulated on the above-mentioned casing.        
Such a centrifuge is also provided with locking means to ensure the holding of the lid in its closed position during the whole cycle of centrifugation.
These locking means have to be moreover adapted to resist to the shocks produced by the rotor, or as the case may be by the cups thereof, in case of separation of the driving shaft at full speed, and to therefore hold the lid in the closed position.
Such locking means are for example described in the document FR-2 951 962.
These locking means comprise a bolt, equipping the casing, which is associated to operating means for its rotational displacement between:                a locking position in which a hook of said bold is associated with a strike carried by the lid for holding the latter in the closed position, and        an unlocking position, in which the bolt is dissociated from said strike to allow the pivotal operation of the lid between its open and closed positions.        
The bolt operating means herein comprise:                a motor shaft that is driven into rotation according to a motor axis of rotation extending parallel to the axis of rotation of the bolt, and        a connecting rod connected, by a first one of its ends, to said bolt by means of a pivoting axis and, by a second one of its ends, to an eccentric mounted on said motor shaft.        
Such a structure allows a relatively effective locking of the bolt in its locking position.
Within this framework, the bolt hook and the bolt/connecting rod pivoting axis are positioned on either side of the bolt pivoting axis, so that a lever arm liable to be exerted on the bolt is opposed to a lever arm liable to be exerted on said bolt/connecting rod pivoting axis.
Furthermore, in the locking position, it is needed that the bolt/connecting rod pivoting axis, the top point of the eccentric and the motor axis of rotation are aligned.
Now, in practice, this need for a precise alignment of three different points of the operating means makes such a structure relatively complex; further, the alignment of the three points is relatively difficult to respect due to the inertia of the gear motors, with a risk about the holding in position of the locking.
Moreover, this structure of the locking means is cumbersome due to the presence of the connecting rod interposed between the bolt and the eccentric. This mechanism is also complex as regards the number of parts, with the resulting problems of reliability and of holding of the locking.
The operation of the bolts, through such a structure of the locking means, further proves to be relatively slow.